Posted
by
kdawson
on Tuesday January 22, 2008 @06:26PM
from the nothing-to-see-here dept.

Linnen writes in to note that one of developers of Sun's open source system tracing tool, DTrace, has discovered that Apple crippled its port of the tool so that software like iTunes could not be traced. From Adam Leventhal's blog: "I let it run for a while, made iTunes do some work, and the result when I stopped the script? Nothing. The expensive DTrace invocation clearly caused iTunes to do a lot more work, but DTrace was giving me no output. Which started me thinking... did they? Surely not. They wouldn't disable DTrace for certain applications. But that's exactly what Apple's done with their DTrace implementation. The notion of true systemic tracing was a bit too egalitarian for their classist sensibilities..."

Thank god apple has a thriving community that is constantly working to fix apple's design decisions. Someone should try building an OS that's entirely community supported. Imagine how productive they would be without apple working against them.

In terms of a "modern" UNIX, a Linux distribution is more "UNIX" than OSX. The filesystem layout is more standard UNIX, the graphical environment is more UNIX, etc etc etc without using add-ons like a non-native X server running on top of Aqua, and the list goes on..

MacOS is a decent system in of itself, but to say it's more UNIX than a Linux distribution is laughable. I mean, c'mon. Get over it. Next you'll say MacOS washes a car better than a sponge..

It's nice that Dtrace works again. But I'm betting a lot more people use After Effects or Premiere. The QT 7.4 update which enables movie rentals from iTunes breaks any render that takes longer than 10 minutes. Thank god DRM is here to protect me from the work I need to do. Wasn't apple supposed to me the machine for media professionals?

The point, which seems to have eluded you, is that while it's great people are fixing DTrace Apple has also broken applications used by far more people and no fix is available for those (nor can it be).

I get the point now. You are making a logical leap that since the community can "fix" something that the sources are freely available for, then they should be responsible for "fixing" everything that Apple may cripple in some way even though all of the sources to things you want fixed are proprietary. Whether or not that is even remotely possible (which you, in fact, state in your reply that it is not), you were able to vent semi-topical frustration with Apple's breaking popular applications. Even got modded "informative" for it somehow. Good for you. When you have the sources for Quicktime, let the community know and someone may fix it for you.

Also, the point that Apple essentially crippled something that was futile to cripple (remember the sources?) may have eluded you.

I am an IT professional, and the common wisdom is to not install updatesthe day, week, or even month that they are released, unless it fixesa problem that you are experiencing. The quicktime 7.4 update has littleto offer to someone in a production environment.Over the years, this has been proved time and time again.I have a graphics studio that is still on 10.4.6, and they arevery happy with it. The studio manager won't let me do mass updatesunless we try it on one machine first, and feel comfortable that

I know they can't fix it (and I do know what DTrace is), I was just giving another example of apple screwing it's customers - and in the QT case, indefensibly screwing it's most loyal and free spending customers. In the QT case, it was probably ignorance rather than malevolence, but still. Maybe it was a bit OT, but thought it as relevant.

Most likely, Apple's intent is to deliver a 'credible effort' to prevent circumvention and/or reverse engineering.

Even though the labels have largely dropped DRM, they still don't like the idea of users having control over digital music. It's part of their DNA. Their whole business revolved around having control over the production and distribution systems, and they just can't contemplate existence without having control over something. The contracts between Apple and the labels reflect that fear, with Apple having the job of making it look like the horses are still in the barn even though the door is open.

Now technically, that's impossible. But my experience with corporate software development has shown me that you can balance 'customers who don't want to know what's impossible' with judicious use of handwavium. You don't have to build a solution that's bulletproof, you just need something that works most of the time. It doesn't matter if there are workarounds, or even if those workarounds are practically trivial for anyone with a technical background, as long as you can't discuss the workaround without using technical terms.

It's sort of an extension of the Sapir-Whorf hypothesis. It's not that your customers can't think about the problem if you lack the vocabulary, it's more that they won't want to think about the problem if they have to spend effort learning how to discuss it intelligently.

So from a contractual standpoint, providing a 'credible effort' is more about obfuscation than actually trying to do the impossible. Apple probably doesn't care if people can work around this issue, as long as the explanation boils down to 'blah blah blah' to aggressively uninformed label executives.

The interesting issue is that nobody can compete with Apple on, say, a music store effectively.

When they add a new iTunes feature, they can change Quicktime to support it or they can disable DTrace so people can't easily reverse it. Nobody else can do that. They're probably not going to get into a DOJ tiff over it, though - Bush [the _ administration] isn't likely to get into it, and Al Gore is on their board.

---- They're probably not going to get into a DOJ tiff over it, though . . .

*sigh*

There are plenty of alternative sources for digital music, almost all of which will play on an iPod and be indexed by iTunes. The ones that don't are formats the market isn't beating down Apple's door to support (Ogg), or which require licensing fees (WMA). All the MP3s you've bought from Amazon play on an iPod. All the tracks you import from a CD will play on an iPod. The iTunes store is a convenience for iPod owners, not a necessity.

Besides, the standard operational definition of a monopoly is that a company can raise prices without losing sales, because consumers don't have credible alternatives. So far, Apple's behavior with regard to pricing is to fight against price increases.

There are credible alternatives to the iPod for people who want a digital music player. There are credible alternatives to the iTunes store for people who want to buy digital music. There are credible ways to get music without a digital music player. Apple has the leading products in the digital music player market, and is one of the leading outlets for digital music, but there is a big-ass difference between being a market leader and being a monopolist engaging in anticompetitive behavior, and the DOJ's attitude toward market leaders in competitive markets is "don't bother me, I have real work to do."

It might even help someone write a subversive program that cannot be traced - create a new executable file with these bits set (or have them set during execution, or whatever), execute this process and you have something running that can't be traced.

If you can't get accurate counter data (on some completely unrelated thing... say, disk accesses, or page faults, or cache hits) because any interrupts that happen whenever a protected process is on top of the run list are silently eaten, that's pretty darned broken.

Look, I understand that Apple cares about their DRM. Fine and dandy, good for them -- but it'd be nice if they could protect it in a way that didn't break DTrace scripts that have nothing to do with trying to hack the DRM in iTunes.

If they're selectively telling this app NOT to log "certain types of traffic", and give no notification of such, or allow the functionality to be restored, then it's CRIPPLED.

I'm so sick of apologists telling me that stuff that's broken is broken for a good reason and that I should be glad someone deigned to allow me to hack it back to some semblance of functionality without getting sued into oblivion!

Come on, this isn't a class struggle. It's Big Business trying to protect their intellectual property. DRM sucks, this is yet another way in which it degrades computer systems. But Apple's just being a company, and their hack to DTrace is actually good coding. Dislike their choice, sure. But there's no epic struggle for humanity here.

We are more forgiving of people who aren't more chronically evil, life just is that way, get over it.

Nobody and nothing is perfect, this does NOT mean that everything imperfect, is equivalent.

Do you divorce your wife for making occasional mistakes? No, only if she is habitually and frequently bad. Are you more forgiving of a son who just occasionally screws up lightly, as opposed to one who does drugs and steals from you and ends up in jail regularly? Of course. Is every political leader who has lied at least once, just as bad as Hitler? Is somebody who beats his wife every day equally bad to somebody who once slapped his wife over 50 years of marriage?

Please, stop with this pretending that all things are equivalent. There is NO double-standard here.

And some others would argue that the struggle against corporations -- against the organizations that let us wring ever more value from ever less labor -- is a cynical struggle to return humanity to living in caves and digging for roots to eat, a golden time when the folks with silver tongues and zero conscience (lawyers, politicians, and related rabble-rousers, the kind who dominate in high school) could always be on top, while socially-misfit four-eyed dweebs with good ideas -- the kind who found and manag

And some would argue that corporations are valuable economic engines that have built-in antisocial tendencies that can never be eradicated, but must be constantly monitored and kept in check. Corporations are powerful entities that resist those efforts, making it a struggle.The struggle between "good" entities and "evil" ones is a mythical recasting of the everyday struggle between good and evil elements of every person. People are impure, institutions are impure. Corporations are a valuable kind of inst

Friend, a corporation is a miniature society. It's an organization of people that divides labor for the purpose of maximizing the welfare of all, subject to an agreed-upon heirarchical distribution scheme. (That is, the wealth it creates is not usually distributed equally.) Society is merely the largest possible corporation, in which we are all, whether we like it nor not, employed.

What you are saying is that the smaller organization we may voluntarily join (e.g. the corporations that employ us) should be policed by and subject to the larger organizations that we are a member of whether we like it or not (e.g. the country in which we are born).

Yeah, well, not by me. I prefer to choose with whom I associate, and to whom I listen. I most definitely do not like the idea of the largest possible organization of which I'm a member, like it or not, enforcing the ultimate rules of my life. I'm much happier if the rules are defined by a smaller organization that I voluntarily join, and which I can voluntarily leave if I don't like the rules.

In a free society, where the largest powerful organizations are much smaller than the entire country, I can find the corner of it that plays by the rules I like. I have choices. I can be mostly who I want to be. In your "social" society, I have no more choices. I have to be what the majority thinks I should be, act accordingly to their morality and expectations.

No thanks! I know my average fellow man too well to think it would be fun to allow him to dictate the terms of my life.

The struggle against corporations may be an important part of the defense of humanity, but some would argue that seemingly innocuous things are often just small, innocuous things, and that to go ape shit about them and blow them out of proportion is characteristic of small minds and spirits.

Some would also argue that getting hung up on the small things and seeing battles to be won therein is a good way to ensure that people never take on any large and not so seemingly innocuous issues, that they self indulgently imagine themselves to be revolutionaries fighting the good fight and propagating righteous and enlightened rhetoric.

And even if these people are totally wrong, it still doesn't excuse the ideologically loaded "classist sensibilities" bullshit. But I'm sure the original poser, err poster, feels good about his awesomeness.

Come on, this isn't a class struggle. It's Big Business trying to protect their intellectual property. DRM sucks, this is yet another way in which it degrades computer systems. But Apple's just being a company, and their hack to DTrace is actually good coding. Dislike their choice, sure. But there's no epic struggle for humanity here.

First, they crippled DTrace, but I did not use DTrace, so I did not speak up.
Then, they came for gettytab, but I did not speak out, because I was happy with Apple's default terminal configuration.
Then, they came for snort, but I was not worried about intrusion detection so I did not speak up.
Next, they came for mkdep, but I did not speak out, because the maid does all my compiling.
Sadly, when it came time for them to use killall, there was nobody left to speak up for me!

EULA: "Sharing is stealing".
BSD licence: "Sharing is not stealing".
GPL2 = "Not sharing is stealing".
GPL3 = "Not sharing is definitely stealing, but just simply sharing is not necessarily not stealing either".

The BSD licence interpreted literally can permit distribution of binaries without Source Code. The BSD people work their backsides off to ensure that nobody does this. The GNU people decided to write their own licence explicitly forbidding it. There is no other word for this except laziness.

Apple is as much the DRM laden threat to open computing as Microsoft is. We may have circumvented this issue this time, but what about the time after that? and after that? Its a cat and mouse game Apple is going to play.

It is DRM'd to only run on Apple hardware. There is nothing technical that prevents it from running on any modern PC since that is indeed what Macs are now. However that won't work, hence there are groups out there that have to hack it to disable that and allow it to run on any hardware.

You can argue till your blue in the face that they need to do this, doesn't change what they are doing. If it wasn't DRM'd, it'd run fine on any hardware that met its technical requirements.

Well sort of, but it is also licensed to only run on Apple hardware, so unless you're planning on breaking the license you don't have a problem. DRM on media attempts to apply licensing to content, which is a slightly different matter. As a Linux supporter I object to users modifying Linux and redistributing it without the source as that violates the license. I don't see why Apple should not only object but take measures to prevent people from violating their license. (Especially given that they are in a bad place economically as their crown jewels is a desktop OS and the desktop OS market is monopolized, which means if they can't bundle their OS with a complete system, there is no long-term way to stay in business unless the courts act effectively against MS... and we all know our court system is way too corrupt for that.)

Look I admit it would be nice if Apple unbundled their OS and hardware, but I'm also smart enough to know that would quickly lead to Apple having to stop developing their OS altogether. I'm also smart enough to see how much collateral damage that would do to open standards and Linux as it would change the market from, 8% OS X and 1% Linux and 80% Windows to 98% Windows in a hurry. MS doesn't need more power to break the market and that is exactly what we'd have if Apple dropped their hardware and OS bundling as a license requirement.

There's no friendship, you're just a fan and Apple rakes in your money. They love this cult like status, some of it is well deserved, their design is unmatched in the computer field. If Mac fans were a little more reserved instead of opening their wallets then Apple would stop and think a bit more.I'm by no means a fan boy, I own a Mac Pro and I run Leopard. They're just tools and even with Apple's flaws I'll still with them until something better appears.

That's because the CEO of Apple wrote and published an open letter on their website expressing his desire to rid their music store of DRM, and the CEO of Microsoft has done no such thing, instead integrating DRM support into their entire audio and video driver stack. (To the detriment of the stability and functionality of the rest of the OS, I might add...) Please, please, let me know when Microsoft (or a major figurehead thereof) takes an official position against DRM. I'll be waiting eagerly.

From the DTrace source (in an #IFDEF APPLE):/*
* If the thread on which this probe has fired belongs to a process marked P_LNOATTACH
* then this enabling is not permitted to observe it. Move along, nothing to see here.
*/

Luckily no malicious programmer will mark their malware's process with this flag!

This reminds me of the bozo bit in the early Macintosh file system. Not much protection, but it did force the attacker to take an action that might be later used to demonstrate intent. Perhaps the P_LNOATTACH serves a similar purpose?

From the DTrace source (in an #IFDEF APPLE):/*
* If the thread on which this probe has fired belongs to a process marked P_LNOATTACH
* then this enabling is not permitted to observe it. Move along, nothing to see here.
*/

Luckily no malicious programmer will mark their malware's process with this flag!

Maybe Apple has a few Macs with a modified DTrace version that _only_ observes processes with this flag set...

You of all people should know that you give up your freedom to use your software and hardware as you wish when you use proprietary software. Apple's continuous attempt to stop people from changing software on their home computers is a good example of how they feel about freedom. They only side with freedom when it is immediately beneficial.

It's like this every time kdawson takes a turn posting stuff to the front page. Wish he'd join up with his natural comrades at digg.com and take the tired rewarmed leftovers of 19th and 20th century politics away with him.

Quote:"So Apple is explicitly preventing DTrace from examining or recording data for processes which don't permit tracing. This is antithetical to the notion of systemic tracing, antithetical to the goals of DTrace, and antithetical to the spirit of open source."

For now, yes... But apple has been in the process of creating cryptographically secure signing and verification of system applications. The next step for them will be to have system tools like this be executed ONLY if they are the unmodified, signed applications that apple originally released.

When that happens, it wouldn't matter if you recompile dtrace - your modified version would just not run.

for info on the current code signing specification from apple (which is pretty much benign for now), see:

You've (like many) completely misunderstood the point of Apple's code signing efforts. It's not to stop unauthorized code from running--Apple is not Microsoft, no matter how you cut it; they don't even have activation, nor any protections on their software besides serial numbers. The real point of code signing is so that when you have a piece of software that claims to be from Company X, you can be sure it's actually from Company X. It's a tool to reduce malware pretending to be legitimate software, not a means for Apple to lock down your computer.

Its main market is for an easy to use home computer and as a creative platform for video editing, graphic design and professional audio.

And software development. Or where did you think the developers of those video editors work and test their code?

If you want a command line you're fully in control of, use Linux or a BSD Unix.

No disagreement there, but it doesn't hurt to remind people that OS X is not that. People often leave Linux for OS X, claiming that it's basically an easier-to-use Linux than Linux, you still have all your stuff, etc. And you can always ssh to a Linux server to do real work.

It's a commercial OS and Apple will do what they like so long as its legal.

The/. summary and most of the/. posters seem to be missing the point of the article. (To be fair, the author wasn't too clear himself. He's done some clarification in the comments section of his article.)

Sure, it's annoying that DTrace can't "see" iTunes. But that's more of a DRM issue. Whether you agree with DRM and Apple's implementation of it or not, this DTrace feature is merely a logical extension of that issue.

The real problem though is that this feature actually does break iTunes. If DTrace probes while the iTunes application happens to be the application currently running on the CPU, the DTrace probe won't run. (It's technically a thread of iTunes' at that moment.) So not only will DTrace not show iTunes, it won't show ANY information until it happens to fire off when iTunes isn't the app running on the CPU.

It is fair to say that Apple has made a change to DTrace that has introduced a bug that they need to fix. It is possible for them to fix that bug while continuing to block using DTrace on iTunes.

The real problem though is that this feature actually does break DTrace. If DTrace probes while the iTunes application happens to be the application currently running on the CPU, the DTrace probe won't run.

In what situation is this a problem if you are not probing iTunes? If you're trying to get info from another program, iTunes won't be the application currently runing on the CPU when the event happens.

If I make a third party app that and Apple allows my app to be traced and reverse engineered when they don't allow it for their own apps, does that mean they've chosen to assist in the reverse engineering of my app? If tracing is bad for their app, why is it ok with mine? Just asking? Could a court ask them?

I just don't see what the big deal with all of this is. Smart people don't touch ITunes, because it's just going to help feed the beast. People seem to have forgotten how Jobs ran Apple the last time he was in charge. He's merely a lot more charismatic than Gates. But they are both equally self-serving.

Yes, it's annoying - every time we examine the system we are now looking at everything except for iTunes (and possibly Spy-WaR3;-). But this issue is about more than just that.

I've introduced DTrace to many companies. While most people love it, some developers of closed source software are concerned about people DTracing their code. DTrace allows customers to gather proof of bugs that are embarrassing, hard to fix, or that the developers have deny existed. I've been asked many times if DTrace can be disabled for an application, usually to avoid negative publicity from the bugs that DTrace will expose. The answer has always been no. It's been great to see developers accept this reality and escelate bug fixing.

This is expected - DTrace visibility should improve overall code quality in IT. Hopefully it will also encourage employers to hire better programmers - since if customers don't use DTrace to point out embarassing bugs, then competitors may. It also erodes reasons to stay closed source - customers can use DTrace to see the code anyway.

Giving developers another option, to disable DTrace visibility, is allowing a backwards step from the future.

It's a real shame that you can't trace iTunes. I was all set to reverse engineer it and use the code to make my own total fucking abortion of a media player. Now I'll have to settle for grafting a horrible GUI onto Mplayer, removing most of the supported formats and making it sleep without releasing the CPU 90% of the time. If I can work out some way to reliably fuck up the contents of the user's iPod, then I doubt anyone will notice the difference.

It will be tricky to make the Windows port twice as horrible though. Maybe I can get it to punch the user in the face every ten minutes?

Leopard's DTrace isn't broken. Apple put in an API for a program to request that debugging & dtrace be disabled for it. Clearly it's there to keep FairPlay from being broken (too easily). Something that commercial developers could understandably want for their software, to prevent keygen hacks, etc.

The link I provide shows a simple way to get around it. Hell, debugging iTunes is directly encouraged in an Apple Technote (linked in the article).

As listed in the article I linked to, you can get around it by trapping the API call in gdb and disabling it.

Actually, Leopard's DTrace is broken, and that was the point of the blog post. Here's the issue: DTrace programs that would normally work and collect valid data will fail if a process is running with Apple's trace-me-not bit set. Forget tracing iTunes or other applications that don't want to be traced. It's that probes that should fire don't as an unintended side-effect of Apple's hack to obscure certain applications.

A much smarter approach would have been for Apple to deny visibility into such a process, but still allow a user to monitor system-level events (e.g. timers and system calls). This would have allowed for the (questionably motivated, and highly circumventable) protection while not damaging DTrace and correctly phrased queries.

DTrace works on processes it's supposed to, and doesn't work on those it's not. I'm happy to agree the implementation of the latter is buggy, but I don't think it's the end of the world or a conspiracy theory. Maybe later the providers can be adapted to more intelligently deal with these closed-off processes to give more consistent results.

Apple decided to put in some measures to keep some software locked-down. The correctness of doing so isn't a technical issue, that's a philosophical one.

DTrace is a wonderful tool: one that's saved me *months* off my PhD work, and I love it. And you have my deepest respect for it. But, I don't take dtrace as a philosophy -- I gave up on software religion a long time ago. Everyone's got their own requirements (e.g. locking down iTunes to keep FairPlay from being cracked -- to keep record producers from leaving iTunes) and they've gotta get them done however they can. Call it mercenary ethics if you want, but we don't all work at Sun with CEOs who get it.

Leopard's DTrace isn't broken. Apple put in an API for a program to request that debugging & dtrace be disabled for it. Clearly it's there to keep FairPlay from being broken (too easily). Something that commercial developers could understandably want for their software, to prevent keygen hacks, etc.

The link I provide shows a simple way to get around it. Hell, debugging iTunes is directly encouraged in an Apple Technote (linked in the article).

As listed in the article I linked to, you can get around it by trapping the API call in gdb and disabling it.

Why are you standing up for Apple in this? By your own admission, DTrace is broken (oh yes, you can get around it, Bah!) Why in the world should you have to do any of that!

DTrace is a system level tool that should work properly on any and every process and thread in the system without smoke and mirrors.

Leopard's DTrace is broken. It does not do what it should.

There's no hating or drama about it. I don't care why they did it, and you're probably right that DRM is the reason. That doesn't mean it's not fubar'd.

The best thing to do now is to make DTrace as useless as possible until Apple removes this limitation.

Every developer reading this who cares about DTrace and wants to be able to use it for system-wide metrics should set the P_LNOATTACH flag in the next point release for their app. Apple won't like it, but if enough developers do it as a form of protest, it would effectively make DTrace/Instruments ineffective, eliminating a bullet-point feature from Leopard.

Back in 2000, if you installed MacsBug on a Mac you couldn't play DVDs. When you opened the DVD Player you got an error message telling you a debugger was installed. In these pre-memory protection days, MacsBug was the only debugger low-level enough to catch a whole mess of problems. Unfortunately, MacsBug was loaded when the system booted, so the only way to play a DVD was to remove MacsBug and restart your machine.

This whole message mess came about because Macrovision didn't want people disabling their protection on video-output (there were Macs you could literally plug into VCRs then), and I suspect it was also to guard the CSS "encryption."

When Blu-ray movies finally show up in Macs, this kind of thing is probably going to get a lot worse than patches to D-Trace.

The real effects seem to be that while a process which sets this flag has control of the system, any DTrace events that fire off during this time will not be detected, as if they never occurred, regardless of whether what is being traced has anything to do with that process. It seems to break a few important(?) idioms used by DTrace users, so that the results returned are not what they should be.

The furor seems to be that this subtle breakage has gone undocumented; and although only iTunes currently uses it, that does not stop other software (including software that should not be there) from using it. That a DTrace developer discovered this, combined with that this is in all likelihood being done for no reason other than that of DRM, is what makes this notable. If I were working on DTrace, I'd probably be pissed too.

Darwin is Apple's stuff. They made it. It is based on BSD, but the BSD license doesn't require them to release the source (does it? IANAL). It is also based on NeXTSTEP, which was acquired by Apple in the 90s.

Apple's record with open source is inconsistent. Sometimes they develop internally and release source (Darwin, Bonjour), sometimes they collaborate with open source projects and share (WebKit with KDE), sometimes they buy out someone's software (Cover Flow), sometimes they steal ideas and never credit original authors (Dashboard).

Apple has its own open source license, the Apple Public Source License, approved by OSI and the FSF. However, they also release under the Apache license as well.

I would say in general, Apple is very open source-friendly, and a lot of open source developers I know have flocked to the Mac. It's just sometimes they have some evil empire corporation actions that make us Apple users shake our heads.

The guy wants Apple to ship a working DTrace. Why should they? To regain community goodwill and get absolution from an official DTrace developer. He left the door open for that. That's the carrot. By publicizing statements on his blog and getting it submitted to Slashdot, he has proved how much trouble he can stir up. By understating the case, he reserves the threat of stating it plainly if they take no action. That's the stick. Now Apple has to weigh community goodwill against DRM dollars and decid